1. Field of the Invention
The present invention relates to a power feeding apparatus that prevents circuit elements from being destroyed due to an applied over load, and to a transporter and a transport system equipped with the power feeding apparatus.
2. Description of the Related Art
Conventionally, many transport systems have been realized in order to transport goods by means of transporters moving along a guide rail, and the efficiency of the transportation of goods within a plant or a warehouse has been increased. Generally, a motor is used to drive such a transporter, and the electric power is supplied to the motor via a feeder line attached along the guide rail.
As for the power feeding apparatus, there are two types, i.e., a trolley type and a non-contacting type. Because less dust is generated and less maintenance service is required, the non-contacting type power feeding apparatus system is frequently used. In the non-contacting type power feeding system, a pickup equipped to the transporter is disposed adjacent to the feeder line, and an induced electromotive force is generated on the coil by means of the electromagnetic coupling between the pickup and the feeder line to supply the electric power.
FIG. 1 is a block diagram showing a conventional non-contacting type power feeding apparatus. In the figure, reference numeral 1 denotes a pickup, which is comprised of a pickup coil L wound around a pickup core (not shown). The pickup 1 is equipped on a transporter or the like and is disposed adjacent to the feeder line 9 connected to an electric power source 11. The feeder line 9 is laid along a guide rail (not shown) or the like disposed within a plant. The transporter is movable along the guide rail. Connected in parallel to the pickup coil L are a resonance capacitor C and a rectifier circuit 4. The resonance circuit 2 is comprised of the coil L and the resonance capacitor C. The output terminals of the rectifier circuit 4 are connected to the input terminals of a constant voltage circuit 40, and the output terminals of the constant voltage circuit 40 become the output terminals U and V of the non-contacting type power feeding apparatus, and at the output terminals U and V, the driving unit of the transporter is connected thereto.
In the non-contacting type power feeding apparatus structured as described above, when AC electric power is supplied to the feeder line 9 connected to the electric power source 11, induced electromotive force is generated on the pickup coil L. The induced electromotive force is resonated in the resonance circuit 2 to obtain maximum electric power, and further, rectified in the rectifier circuit 4, converted into electric power having constant voltage characteristic by the constant voltage circuit 40 and outputted from the output terminals U and V. The electric power outputted from the output terminals U and V is supplied to the driving unit of a transporter or the like (not shown) and the transporter is driven thereby.
In the non-contacting type power feeding apparatus described above, when the rectifier circuit 4 or the constant voltage circuit 40 is opened, or in case the load 10 has an inverter and when the circuit is short circuited, an overcurrent flows through the pickup coil L and resonates resulting in generation of an overvoltage on the resonance capacitor C. Accordingly, there is a danger that circuit elements may be destroyed or burnt out due to overheat. Accordingly, in order that a service person carries out an inspection and repair service on a point in which the abnormality has occurred, it is necessary to shut down the electric power source 11 even when the other non-contacting type power feeding apparatuses are normal.
As described above, in the conventional non-contacting type power feeding apparatus, when an overcurrent flows through the pickup coil L and resonates, there is a danger that circuit elements may be destroyed or burnt out due to an overvoltage generated on the resonance capacitor C. In order to solve this problem, a non-contacting type power feeding apparatus is disclosed in Japanese Patent Application Laid-Open No. 11-164497 (1999). In the above-mentioned non-contacting type power feeding apparatus, a thermo-responsive mechanical latch relay having a heat-sensing device installed adjacent to the pickup coil L and a contact provided between the both ends of the pickup coil L or between the output terminals of the rectifier circuit 4, which maintains the contacting state even when the electric power supply is discontinued, is provided. When the temperature of the pickup coil L exceeds a predetermined temperature, the contact of the mechanical latch relay is closed to establish a short circuit between the both ends of the pickup coil L or between the output terminals of the rectifier circuit 4 so that the circuit elements are prevented from being destroyed or burnt out.
According to the non-contacting type power feeding apparatus disclosed in Japanese Patent Application Laid-Open No. 11-164498 (1999), when an abnormality has occurred, even when a service person has not completed the inspection and repair service yet, but when the temperature of the pickup coil L decreases lower than the predetermined value, since the contact of the thermostat opens automatically to return to the original position, there is a danger that the service person may get an electric shock, and also, abnormalities due to the identical cause may be repeated.
In order to solve the troublesomeness and danger residing in the latch-releasing service of the above-mentioned mechanical latch relay, a non-contacting type power feeding apparatus is disclosed in Japanese Patent Application Laid-Open No. 11-164498 (1999). In the above-mentioned non-contacting type power feeding apparatus, a thermostat having a contact between the both ends of the pickup coil L or between the output terminals of the rectifier circuit 4, and a heat-sensing device adjacent to the pickup coil L is provided. When the temperature of the pickup coil L exceeds a predetermined value, the contact is closed to prevent the circuit elements from being destroyed, and when the temperature decreases lower than the predetermined value, the contact opens automatically to restart supplying the electric power.
According to the non-contacting type power feeding apparatus disclosed in Japanese Patent Application Laid-Open No. 11-164498 (1999), when am abnormality has occurred, even when a service person has not completed the inspection and repair service yet, but when the temperature of the pickup coil L decreases lower than the predetermined value, since the contact of the thermostat opens automatically to return to the original position, there is a danger that the service person may get an electric shock, and also, abnormalities due to the identical cause may be repeated.
The present invention has been made to solve the above-described problems. Accordingly, it is an object of the invention to provide a power feeding apparatus equipped with a switching element connected between the output side terminals of a rectifier circuit and the output terminals of the power feeding apparatus, which becomes into a discontinuous state when an overvoltage exceeding a predetermined value has occurred at the both ends of the pickup coils due to a short circuit of a load or the like. Accordingly, the power feeding apparatus according to the invention enables to prevent an overcurrent from flowing through the load, and enables to prevent the circuit elements from being destroyed or burnt out due to an overcurrent generated in the pickup coils or an overvoltage generated in the resonance capacitor. Further, the power feeding apparatus according to the invention enables to make the switching element to become into a discontinuous state without any delay at an occurrence of instantaneous overvoltage.
Further, since the above-mentioned switching circuit is structured so that the electric power is fed from the output side terminals of the rectifier circuit, it is possible to provide a power feeding apparatus that enables to receive the electric power even when the switching element has become into a discontinuous state at an occurrence of an abnormality, and enables the non-contacting type power feeding apparatus itself to indicate an alarm of the abnormality even when an abnormality has occurred.
Furthermore, in addition to the above, it is another object of the invention to provide a power feeding apparatus in which the above-mentioned switching control circuit is equipped with a communication unit enabling the switching element to maintain the discontinuous state and to be controlled by means of a remote control to avoid a danger accompanying the releasing service of the switching element and a danger of a service person due to automatic resetting of the switching element.
Still further, it is another object of the invention to provide a power feeding apparatus in which a temperature sensor connected to the above-mentioned switching control circuit is provided adjacent to the pickup coils, which enables the switching element to become into a discontinuous state to prevent the circuit elements from being destroyed or burnt out even when the voltage at the both ends of the pickup coils is lower than a predetermined value, in case the temperature of the pickup coils exceeds a predetermined value due to a temperature rise around the pickup coils or an increase of the electric power or the like.
Still furthermore, it is another object of the invention to provide a power feeding apparatus in which a fuse is provided at the connecting point between the pickup coils and the switching control circuit so that the fuse is opened to prevent the circuit elements from being destroyed due to an applied overcurrent or overvoltage even when an abnormality has occurred in the switching control circuit, the switching element has become into uncontrollable and an overcurrent has flowed through the circuit elements.
Further again, it is another object of the invention to provide a transporter equipped with the above-mentioned power feeding apparatus that enables to respond to an abnormality occurred while the power is supplied and to provide a stable drive, and a transport system that includes the above-mentioned transporter and a feeder line for supplying the electric power to the power feeding apparatus mounted on the transporter to provide a stable drive.
A power feeding apparatus according to the first invention is a power feeding apparatus, comprising: pickup coils for generating induced electromotive force; a rectifier circuit for rectifying the induced electromotive force generated on the pickup coils; output terminals for outputting the output electric power from the rectifier circuit; a switching element connected between the output terminals of the rectifier circuit and the output terminal; and a switching control circuit connected to the pickup coils and the switching element for carrying out ON/OFF control of the switching element corresponding to the voltage at the both ends of the pickup coils by obtaining the electric power from the output side terminals of the rectifier circuit.
A power feeding apparatus according to the second invention is a power feeding apparatus as described in the first invention, further comprising a temperature sensor connected to the switching control circuit for outputting signals corresponding to the temperature of the pickup coils, wherein the switching control circuit carries out ON/OFF control of the switching element corresponding to the output signals of the temperature sensor.
A power feeding apparatus according to the third invention is a power feeding apparatus as described in the first invention or the second invention, further comprising a fuse at a connecting node between the pickup coils and the switching control circuit.
A power feeding apparatus according to the fourth invention is a power feeding apparatus as described in the first invention or the second invention, wherein said switching control circuit comprises a communication unit.
A transporter according to the fifth invention is a transporter equipped with any one of the power feeding apparatuses described in the first invention through the fourth invention, and is driven by the electric power supplied by the power feeding apparatus.
A transport system according to the sixth invention comprises a feeder line connected to an electric power source for generating the induced electromotive force on the pickup coils, and a transporter described in the fifth invention.
In the power feeding apparatus according to the first invention, when an overvoltage exceeding a predetermined value has occurred at the both ends of the pickup coils due to a short circuit or the like of a load, the switching element is made to become into a discontinuous state by the switching control circuit, and it is possible to prevent any overvoltage from flowing through the load without stopping the electric power source. Further, it is possible to prevent the circuit elements from being destroyed or burnt out due to an overcurrent generated on the pickup coils or an overvoltage generated in the resonance capacitor. Furthermore, it is possible to make the switching element to become into a discontinuous state without any delay at an occurrence of instantaneous overvoltage.
Still further, even when the switching element has become into a discontinuous state at an occurrence of an abnormality, it is possible that the switching control circuit make the power feeding apparatus itself to maintain the indication of the abnormality and to maintain the switching element in discontinuous state.
In the power feeding apparatus according to the second invention, even when the voltage generated in the pickup coils is lower than the predetermined value, but when the temperature of the pickup coils exceeds the predetermined value due to a temperature rise around the pickup coils or an increase of current or the like, the switching element becomes into a discontinuous state to prevent the circuit elements from being destroyed or burnt out.
In the power feeding apparatus according to the third invention, even when an abnormality has occurred in the switching control circuit, and the switching element has become into uncontrollable and an overcurrent flows, the fuse is opened to prevent the circuit elements from being destroyed or burnt out due to an applied overcurrent or overvoltage.
In the power feeding apparatus according to the fourth invention, it is possible to control the switching element by means of a remote control. Accordingly, it is possible to eliminate a danger and troublesomeness accompanying the releasing service of the switching element at a position where the power feeding apparatus in which the abnormality has occurred is installed, and to eliminate a danger or the like of a service person due to automatic resetting of the switching element.
In the transporter according to the fifth invention, it is possible to respond to an abnormality occurred while the electric power is supplied and to provide a stable drive.
In the transport system according to the sixth invention, it is possible to provide a stable drive and effective transportation of goods.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.